The strategy of feeding large doses of antigen to prevent or reverse intestinal inflammatory diseases has not been as successful as was anticipated. This should not eliminate consideration of allergen desensitization by induction of oral tolerance as a mechanism to prevent allergic gastrointestinal disease in response to food antigens. Our preliminary data demonstrate that low dose of antigen delivered from mother to child in breast milk induces antigen-specific Tregs in gut-draining lymph nodes. Perhaps the acquisition of antigen from breast milk provides the perfect context (i.e. TGF[unreadable] and retinoic acid) to result in focused protection by Treg in the exact site where it is needed, the gastrointestinal tract. The goals of this grant application are to further the understanding of how breast milk transmission of antigen elicits mucosal Treg responses, and to determine the potential of breast-milk antigen induced Tregs to influence allergic responses to food antigens in the intestine. It has been recently determined that retinoic acid enhances TGF[unreadable]-dependent differentiation of na[unreadable]ve CD4+ T cells into FosP3+ Tregs and directs their homing to the gut. One of the major functions of breast milk and breast milk macrophages is to deliver dietary lipids and fat-soluble vitamins (e.g. vitamin A [retinol] and its metabolites) to nursing offspring. Moreover, vitamin A levels in the maternal diet are known to affect development of the immune system in breastfed neonates. Thus, we hypothesize that during breastfeeding, offspring acquire allergen which elicits CD4+ T responses under the influence of breast milk TGF[unreadable] and maternal vitamin A, inducing antigen-specific Tregs in the neonatal gastrointestinal tract. We propose that this maternal transfer mechanism to elicit Tregs could mediate antigen-specific protection from allergic gastrointestinal disease in offspring. To explore the validity of this hypothesis and to determine its biological relevance, we propose the following Aims: SPECIFIC AIM 1. Determine the capacity of breast milk to induce antigen-specific Tregs via delivery of retinoic acid (TGF[unreadable] and allergen) to the neonatal gastrointestinal tract;and SPECIFIC AIM 2. Determine the capacity of breast milk antigen induced Tregs to suppress intestinal inflammation in vivo using a model of food allergen induced diarrhea. If we find that this maternal breast milk antigen-induced population of Tregs survives after weaning and is functional in suppressing food allergy, it will be important to consider what appears to be a safe strategy for mothers to induce protective immune responses in their offspring. Mothers, particularly those that are nursing, are highly motivated to improve the health of their children. If it is possible to modify breast milk content to enhance development of mucosal tolerance in neonates, this could be an effective strategy to prevent or attenuate immune-mediated inflammatory diseases in the intestine. The relevance of this project to public health is based on the fact that the prevalence of food allergy appears to be increasing;yet there are no definitive therapies. This exploratory project aims to define whether induced oral tolerance in neonates can provide long term protection from inflammatory responses to food allergens in the gut. The strategy is based on the concept that the best way to prevent detrimental immune responses to food is to maximize desensitization to allergens as early in life as possible, before pathogenic antigen-specific T and B cell memory is established.